1. Field of the Invention
The present invention relates to dielectric imaging sheets, and particularly dielectric imaging sheets useful in electrographic imaging wherein a particulate solid, e.g., a filler, is present in the dielectric layer of the imaging sheet. The present invention also relates to an electrographic imaging process using such a dielectric imaging sheet.
2. Description of the Prior Art
Dielectric imaging sheets for use in electrographic imaging are well known. Generally, the dielectric sheets comprise a dielectric layer which contains a solid particulate. The particulate material can be organic or inorganic. Several reasons are described in the prior art for adding such particulate material to the dielectric coating. For example, the particulate solid material can be added as an antiblocking agent, matting agent, or simply as a filler material to reduce the volume of resin needed for the dielectric coating. Suitable solid particulates, of any desirable particle size distribution, can be chosen from such materials as titanium dioxide, calcium carbonate, lithopone, clay, talc, silica, starch or wax.
A drawback to using such particulate solids, and especially amorphous silica, is that moisture adsorbs readily to the surface of the particulate solid. The moisture on the particle surface serves as a site for a short circuit in a nib or stylus type electrographic printer/plotter. As one stylus is short circuited, the available current to surrounding multiplexed styli is diminished, thereby transferring little or no charge to the dielectric sheet in the area of the short circuited styli. The visual effect of such an area that has been developed with liquid toner is one of low or no density. In solid black areas, the defects appear as short white lines perpendicular to the machine direction.
The provision of a dielectric imaging sheet which would be free of such potential imaging defects would be of great importance to the art. The elimination of such defects would greatly enhance the commercial viability of the dielectric imaging sheet, as well as its use in electrographic imaging processes.
Accordingly, it is an object of the subject invention to provide a novel dielectric imaging sheet which substantially precludes moisture induced image defects.
Another object of the subject invention is to provide a novel dielectric imaging sheet which has a particulate solid incorporated in the dielectric layer, which solid has been specially treated.
Still another object of the subject invention is to provide a novel dielectric imaging sheet useful in electrographic imaging and which has a particulate solid incorporated in the dielectric layer, which solid absorbs very little water.
Yet another object of the subject invention is to provide an electrographic imaging process which utilizes such a dielectric imaging sheet.
Still another object of the present invention is to provide a process for fromulating such a dielectric imaging sheet.
These and other objects, as well as the scope, nature and utilization of the invention, will be apparent to those skilled in the art from the following description and the appended claims.